Add multiboot header and test read some info

src/head.asm

@@ -4,7 +4,7 @@ MEMINFO     equ  1<<1                   ; provide memory map
 FLAGS       equ  MBALIGN | MEMINFO      ; this is the Multiboot 'flag' field
 MAGIC       equ  0x1BADB002             ; 'magic number' lets bootloader find the header
 CHECKSUM    equ -(MAGIC + FLAGS)        ; checksum of above, to prove we are multiboot
- 
+
 ; Declare a header as in the Multiboot Standard. We put this into a special
 ; section so we can force the header to be in the start of the final program.
 ; You don't need to understand all these details as it is just magic values that
@@ -15,7 +15,7 @@ align 4
 	dd MAGIC
 	dd FLAGS
 	dd CHECKSUM
- 
+
 ; Currently the stack pointer register (esp) points at anything and using it may
 ; cause massive harm. Instead, we'll provide our own stack. We will allocate
 ; room for a small temporary stack by creating a symbol at the bottom of it,
@@ -25,7 +25,7 @@ align 4
 stack_bottom:
 resb 16384
 stack_top:
- 
+
 ; The linker script specifies _start as the entry point to the kernel and the
 ; bootloader will jump to this position once the kernel has been loaded. It
 ; doesn't make sense to return from this function as the bootloader is gone.
@@ -42,7 +42,7 @@ _start:
 	; you get to make the entire system yourself. You have absolute and complete
 	; power over the machine, there are no security restrictions, no safe
 	; guards, no debugging mechanisms, there is nothing but what you build.
- 
+
 	; By now, you are perhaps tired of assembly language. You realize some
 	; things simply cannot be done in C, such as making the multiboot header in
 	; the right section and setting up the stack. However, you would like to
@@ -51,17 +51,20 @@ _start:
 	; such code. C doesn't expect much at this point and we only need to set up
 	; a stack. Note that the processor is not fully initialized yet and stuff
 	; such as floating point instructions are not available yet.
- 
+
 	; To set up a stack, we simply set the esp register to point to the top of
 	; our stack (as it grows downwards).
 	mov esp, stack_top
- 
+
+	push eax 		; Multiboot magic number
+	push ebx		; Multiboot info struct
+
 	; We are now ready to actually execute C code. We cannot embed that in an
 	; assembly file, so we'll create a kernel.c file in a moment. In that file,
 	; we'll create a C entry point called kernel_main and call it here.
 	extern kernel_main
 	call kernel_main
- 
+
 	; In case the function returns, we'll want to put the computer into an
 	; infinite loop. To do that, we use the clear interrupt ('cli') instruction
 	; to disable interrupts, the halt instruction ('hlt') to stop the CPU until

src/kern.c

-#include <stdbool.h> /* C doesn't have booleans by default. */
+/*
+  kern.c is where the c code starts, as invoked by our heading
+  assembly. It should only contain high level code
+*/
+
+#include <stdbool.h>
 #include <stddef.h>
 #include <stdint.h>
 
@@ -9,11 +14,10 @@
 #include "gdt.h"
 #include "idt.h"
 #include "test.h"
+#include "multiboot.h"
 
-#if defined(__cplusplus)
-extern "C" /* Use C linkage for kernel_main. */
-#endif
-void kernel_main() 
+// The parameters passed here ultimately come through the bootloader
+void kernel_main(multiboot_info* mbd, uint32_t magic)
 {
     /* Initialize terminal and serial interfaces */
     terminal_initialize();
@@ -29,6 +33,11 @@ void kernel_main()
     terminal_writestring("Hello, kernel World!\n");
     //serial_writestring("Second Serial Test\n");
 
+    serial_hexstring(&magic, 4);
+    serial_writestring("\n");
+    serial_hexstring(&(mbd->flags), 8);
+    serial_writestring("\n");
+
     // Enable paging of memory. For now there is only one virtual
     // memory space defined by page_dir
     page_directory_entry* page_dir;